Messi, Suárez and Vidal re-join group the training to prepare the Catalan Derby after the holiday.
The three South Americans had been granted a slightly longer break than their European teammates, with the rest of the squad having had their first post-Christmas training session on December 29.
Elsewhere in the squad, Valverde will be unable to call upon neither Ousmane Dembele nor Arthur Melo for the Espanyol match, while Marc-Andre ter Stegen is a serious doubt.
In Thursday afternoon's session, the first of 2020, Valverde included Inaki Pena, Alex Collado, Carles Perez and Ansu Fati.